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What is split-brain and how do I recover?

Hvad er split-brain, og hvordan gendanner jeg det?

Last modified date: 2025-05-28

Applicable Products

QuTS hero h5.3.0 or later
High Availability Manager 1.0 or later

Definition and Cause

In a high-availability (HA) cluster, split-brain occurs when both nodes lose communication with each other but remain operational independently, and both nodes have assumed the active node role. This may cause data inconsistency or corrupted shared storage, because each node may attempt to take control of shared resources simultaneously.

Common causes of split-brain include:

Network disconnection between the nodes in the cluster
Failure of the heartbeat connection
Unstable or inconsistent network paths

Solution

Fix the network connection between the nodes.
First check and restore the network connection between the two nodes (for example, the heartbeat connection, switches, network settings).
Only after the connection is restored can the system proceed to verify the cluster status.
Let the system automatically detect the split-brain status.
1. Once the nodes reestablish communication, the system exchanges status information between the two nodes.
2. If both nodes have assumed the active node role, the system identifies it as a split-brain condition.
3. To prevent data corruption, the system stops most services (such as SMB, iSCSI) and displays an error message indicating that split-brain has occurred.
Recover from split-brain via High Availability Manager.
1. Open High Availability Manager.
2. Click Recover from Split-Brain to launch the recovery wizard.
  In the wizard, you can choose one of the following recovery options:
  - Option 1: Preserve data on one node only
    Select the node to keep, and the other node will be wiped and reset as the passive node. The system will then resynchronize the HA cluster.
    This option is suitable when you clearly know which node has the correct data and want to restore the cluster quickly.
  - Option 2: Preserve data on both nodes
    If both nodes contain important data, the system allows one node to resume services first, while the other node is removed from the cluster.
    After verifying and reconciling the data, you can manually rejoin the removed node to the cluster.
Optional: Minimize future split-brain by enabling a quorum server.
If the nodes disconnect from each other but remain connected to the network, a quorum server can still monitor the individual nodes and relay their statuses with each other. This helps reduce the chance of split-brain.
You can configure a quorum server by going to High Availability Manager > Settings > Failover Policy > Quroum Server.

Anvendelige Produkter

QuTS hero h5.3.0 or later
High Availability Manager 1.0 or later

Definition og Årsag

I en høj-tilgængelighed (HA) Klynge, split-brain opstår, når begge noder mister kommunikation med hinanden, men forbliver operationelle uafhængigt, og begge noder har antaget rollen som aktiv node. Dette kan forårsage datainkonsistens eller korrupte delte Lager, fordi hver node kan forsøge at tage kontrol over delte ressourcer samtidig.

Almindelige årsager til split-brain inkluderer:

Netværksafbrydelse mellem noderne i Klynge
Fejl i heartbeat-forbindelsen
Ustabile eller inkonsistente netværksstier

Løsning

Fix netværksforbindelsen mellem noderne.
Kontroller og gendan først netværksforbindelsen mellem de to noder (for eksempel heartbeat-forbindelsen, switches, netværksindstillinger).
Kun efter forbindelsen er gendannet kan systemet fortsætte med at verificere Klynge status.
Lad systemet automatisk detektere split-brain status.
1. Når noderne genopretter kommunikation, udveksler systemet statusinformation mellem de to noder.
2. Hvis begge noder har antaget rollen som aktiv node, identificerer systemet det som en split-brain tilstand.
3. For at forhindre datakorruption stopper systemet de fleste tjenester (såsom SMB, iSCSI) og viser en fejlmeddelelse, der angiver, at split-brain er opstået.
Gendan fra split-brain via High Availability Manager.
1. Åbn High Availability Manager.
2. Klik Gendan fra Split-Brain for at starte gendannelsesguiden.
  I guiden kan du vælge en af følgende gendannelsesmuligheder:
  - Mulighed 1: Bevar data på kun én node
    Vælg den node, der skal bevares, og den anden node vil blive slettet og nulstillet som den passive node. Systemet vil derefter resynkronisere HA Klynge.
    Denne mulighed er passende, når du klart ved, hvilken node der har de korrekte data og ønsker at gendanne Klynge hurtigt.
  - Mulighed 2: Bevar data på begge noder
    Hvis begge noder indeholder vigtige data, tillader systemet, at én node genoptager tjenester først, mens den anden node fjernes fra Klynge.
    Efter verifikation og afstemning af data kan du manuelt genindtræde den fjernede node til Klynge.
Valgfrit: Minimer fremtidig split-brain ved at aktivere en quorum-server.
Hvis noderne afbrydes fra hinanden, men forbliver forbundet til netværket, kan en quorum-server stadig overvåge de enkelte noder og videresende deres status til hinanden. Dette hjælper med at reducere chancen for split-brain.
Du kan konfigurere en quorum-server ved at gå til High Availability Manager > Indstillinger > Failover Politik > Quorum Server.

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